But Pythagoras did not proceed in this experiential manner in the discovery of his theorem. He constructed and he counted, and when he did that he acted on postulates: “If this is a right-angled triangle and if that be a square, so,”--and this is just what is done in every science. The general propositions are, “If the relations remain the same as formerly the moon must rise to-morrow at such and such a time.” “If this step in a deduction is not false, if it is well grounded at this point, if it really refers to x, it follows....” In his procedures the criminalist does exactly the same thing. What he must be skeptical about is the postulates from which he starts. Section 26. (d) The Empirical Method in the Study of Cases. Properly to bound our discussion of Humian skepticism, a few words have to be said concerning the empirical method of the sciences. We will call those laws purely empirical which, in the study of nature, yield regularities that are demonstrated by observation and experiment, but upon which little or no reliance is placed with regard to cases which differ considerably from the observed. The latter is done because no reason is seen for the existence of such laws. The empirical rule is, therefore, no final law, but is capable of explaining, especially when true, e.g., the succession of a certain condition of weather from certain meteorological signs, the improvement of species through crossing, the fact that some alloys are harder than their components, and so on. Or, to choose examples from our own field, jurisprudence may assert as empirical law that a murderer is a criminal who has gone unpunished for his earlier crimes; that all gamblers show such significant resemblances; that the criminal who has soiled his hands with blood in some violent crime was accustomed to wipe them on the underside of a table; that the slyest person generally perpetrates some gross stupidity after committing a serious crime, and so renders discovery simpler; that lust and cruelty have a certain relation; that superstition plays a great rôle in crime, etc.